1. Field of the Invention
This invention relates to nuclear power generating plant structures, and more particularly, to a totally submersible platform and containment system for a nuclear power generating plant.
2. Description of the Prior Art
Large nuclear power generating plants are currently sited on land near a water supply necessary for use in evaporative cooling of their associated steam condensers. Competitive land and water uses are making it extremely difficult to procure new land sites for nuclear generating plants and their transmission systems. The unique features of each land site also make it difficult to introduce standardization and "mass" production methods into nuclear power plant design so as to benefit from assembly line production techniques. Particular difficulties with land-sited nuclear power generating plants are:
1. engineering and social conflicts due to the safety and aesthetic characteristics of nuclear power generating plants; PA1 2. the environmental impact of nuclear power generating plants on the water resources in their locale due to their need to reject heat; and PA1 3. the need for isolation of nuclear power generating plants from potential ground motions resulting from seismic events in the vicinity of the plant location.
One possible solution to these difficulties can be effected by placing the plant underground. Several recent studies of this type of siting have indicated that the cost penalties involved do not warrant the potential benefits. The studies also suggest a requirement for necessary geological siting criteria which may not exist in many locations. Also, underground siting does not provide in itself for seismic isolation.
Another possible solution to land siting of nuclear power generating plants, particularly for situations where electrical energy use centers are located near the ocean, is the employment of offshore surface mooring of a floating nuclear power plant, such as is incidentially shown in PERRY, et al. (U.S. Pat. No. 3,794,849). However, obvious major problems arise in such a design from meteorological, surface, and artificial causes.
An attractive alternative to either land siting or offshore surface mooring of a nuclear power plant is the employment of an underwater mooring site. Such a location would protect the plant from adverse meteorological and surface conditions, as well as provide greater isolation from potential ground motions due to seismic activity. Further, undersea siting of nuclear power plants would minimize the danger of theft or sabotage of nuclear materials, since special equipment is required in order to gain access to the submerged plant. Further still, such siting offers several engineering advantages over alternative methods. For example, all nuclear reactors of the water-cooled steam generator type require vast amounts of water to cool their associated steam condensers. For higher efficiency in generating electrical power, this cooling water should have as low a temperature as possible. Further, discharged cooling water should be remixed with its source as quickly and efficiently as possible in order to reduce any impact on the environment due to thermal pollution.
Undersea siting of a nuclear power plant simply and easily meets the above criteria: the supply of cooling water is virtually unlimited, the water temperature at a depth of a few hundred feet is significantly lower than the surface temperature, and efficient remixing of effluent cooling water is readily achieved by convection currents.
A further engineering advantage of undersea siting over alternate methods is the presence thereby of a virtually unlimited heat sink for the reactor in the event of a loss-of-coolant accident, thus preventing dangerous overheating of the reactor core.
SCHANZ, (U.S. Pat. No. 3,115,450) discloses a nuclear reactor situated within a small spherical containment pressure vessel for siting on land, but this embodiment, unlike the present invention, is not believed to be designed to withstand the very large external pressures present at even a few hundred feet beneath a body of water.
BRAY, (U.S. Pat. No. 3,118,818) also shows a submersible nuclear thermoelectric power plant for use in low power (approximately 50 kilowatts) situations, but this design is not believed to be feasibly expandible to the size (approximately 3400 megawatts) necessary to provide sufficient power to offset the cost of construction of such a plant.
It should be appreciated that while spherical pressure vessels for nuclear reactors are described in the prior art, as in HAFTKE, (U.S. Pat. No. 3,087,883), and also that underwater pressure spheres are well known, as in MOUTON, JR., (U.S. Pat. No. 4,004,429), the prior art does not show the combination of elements of the present invention, as more fully discussed herein. In the present invention, the spheres used must not only be able to withstand the large external pressure of the surrounding body of water, but also the internal steam pressure that might occur in the event of a loss-of-coolant nuclear accident.
A loss-of-coolant nuclear accident may occur when a failure happens somewhere in one or more of the coolant loops of a nuclear reactor. In such a situation, the water normally in and around the reactor is vaporized by the heat generated by the reactor, thereby increasing the internal pressure of the enclosing containment sphere tremendously.
It should be further appreciated that although submersible sea platforms of various types are shown in the art, as in GIBSON, et al. (U.S. Pat. No. 3,486,343) and British Patent No. 963,083, the present invention shows a configuration of spherical pressure vessels housing a nuclear steam power generating plant mounted on a platform for total submergence which is unique. The structure of the present invention is particularly rigid, strong, and stable, and the preferred embodiment provides for direct access from any one pressure sphere to the adjacent spheres.
It is therefore an object of this invention to provide a safe and convenient means to house a nuclear power generating plant beneath a body of water.
A further objective is to isolate a nuclear power generating plant from potential ground motion resulting from seismic events in the vicinity.
Another object is to increase the thermal efficiency of such a plant by submerging the plant at depths having a significantly colder temperature than does the surface.
Still a further object of this invention is to provide for more efficient dissipation of the heat rejected from the plant's condensers, due to convection mixing of the effluent waters with the surrounding body of water.
Yet another object is to reduce the demands on limited water supplies which a land-sited plant requires.
The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objectives and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which the presently preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only, and are not intended as a definition of the limit of the invention.